Endoscopic devices for surgical or diagnostic procedures are already known, which are operated by the surgeon who directly imparts to the device its forward motion through the patient's body. These devices are generally associated with surgical and/or diagnostic instruments needed to complete various procedures, e.g. micro-arms, micro-cameras and/or laser emitters.
Endoscopic devices of this type, but capable of autonomous or semi-autonomous locomotion through the body cavity of a patient are described, for instance, in U.S. Pat. No. 5,398,670, U.S. Pat. No. 5,906,591 and WO02/068035. The endoscopic device described in these documents substantially consists of a tubular body of variable length with front and rear end portions equipped with anchoring means that enable said front end portion or rear end portions to become temporarily and alternately attached to the wall of the body cavity, thereby enabling the forward motion of the device.
In particular, the variable-length tubular body of the endoscopic device described in the above-mentioned documents is in the form of a bellows-shaped tube and is consequently capable of being extended or contracted by means of air injected therein or aspirated therefrom. In the above-mentioned patent application PCT n. WO02/068035, the device is anchored to the wall of the body cavity by clamping means associated with the front and rear end portions of the device and selectively enabled by an external control unit in synchronism with the successive extensions and contractions of the bellows-shaped tubular body. The aforementioned clamping means are enabled by pneumatic actuating means that, in the preferred embodiment of the invention, also consist of bellows-shaped members.
When it is extended, a positive pressure is created inside the bellows by means of compressed air, thereby obtaining an elongation proportional to the pressure therein, while the bellows are contracted by progressively reducing the pressure inside the bellows, until some degree of vacuum is created.
In order to overcome the functional limitations of the bellow-shaped endoscopic devices due to its relative extendibility and friction between its outer surface and the walls of the body cavity, which have a negative effect on the device's efficiency of locomotion, EP-A-1792561, in the name of the same applicant, discloses an endoscopic device wherein the tubular body has an high extensibility an a low friction coefficient in such a way to prevent the tissue forming the body cavity wall to be dragged and hence ensuring an effective forward movement of the device.
According to this patent application, the tubular body of the endoscopic device is made of a low hardness elastomeric material, for example Shore A-10 silicone, and incorporates a reinforcement structure distributed along its length that is substantially rigid in the radial direction and yielding in the axial direction. In a particularly preferred embodiment, the reinforcement structure consists of a pair of coaxially aligned springs with coils wound crosswise to one another, incorporated within its thickness. The presence of the springs prevents the tubular body from swelling sidewards, while the inverted winding of the springs prevent the body from rotating during the extension. In another embodiment of the invention the reinforcement structure consists of equally spaced rings coaxially incorporated in the tubular body wall.
The production of the above mentioned tubular body comprises moulding a silicone tubular element, constituting the air containment part, and placing the springs o the array of rings around it. A tubular silicone layer is then moulded on the tubular element to prevent the sliding of the elements forming the reinforcement structure and the direct contact thereof with the intestine tissue.
A production defect, such as a blister or a tearing made during the tubular body extraction from the mould, could cause air to enter between the tubular member and the outer tubular layer thus forming an air bubble.
Due to its chemical nature, silicone does not adhere to metal reinforcement structure within the tubular body wall and, therefore, the interface between the surface of said structure and the silicone material over it forms a preferential channel for flowing out air from the tearing. When the reinforcement structure is formed by helicoidal springs, once air is entered in the meatus between spring coil and silicone, air tends to travel along the spiral all over its length forming a spiral-shaped swelling. When the pressure is high enough, the force acting on the interface is so great as to cause the outer silicone layer to detach from the inner silicone layer, this resulting in the formation of an air bubble as shown in FIG. 1. Depending on its size, the bubble could give raise to a barotrauma, i.e. an injury caused by an excess pressure on the intestine walls caused by air or also an air filled ball. Walls stretch until tearing occurs with consequent pain and bleeding and, in most serious cases, intestine wall breaking. Furthermore, the formation of an air bubble may prevent the device from being withdrawn from the intestine, because it is not sure that if the air flow is stopped, the phenomenon would be reversible. As a matter of fact, the partial reduction of the internal pressure shortens the tubular body and this might cause the closure of the tearing, whereby the air bubble would be kept in an inflated condition.